William arthur thoms



UNITED STATES PATENT OFFICE.

ASSIGNOR TO THE BRIGHT PLATINUM PLATING COMPANY, (LIMITED,)

OF SAME PLACE.

DEPOSITION OF PLATINUM BY ELECTRlCiTY.

SPECIFICATION forming part of Letters Patent No. 367,731, dated August 2, 1887.

Application filed August 31, 1886. ,Serial No. 212,331. (No specimens.)

To all whom it may concern.- 7

Be it known that I, W ILLIAM ARTHUR TiIoMs, a subject of the Queen of Great Britain, residing at 44 St. Oswalds Road, \Vest Brompton, London, in the county of Middlesex, Eng land, electrician, have invented certain new and useful Improvements in the Deposition of Platinum by Electricity; and I do hereby declare that the following is a full, clear, and exact description of the invention, which will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to the deposition of metallic platinum upon metal or other suitable substanee by means of any suitable and well-known electrotyping or plating arrangement and a specially-prepared bath; and this invention has for its object the deposition of the platinum with greater economy, solidity, and in greater perfection than in the methods hitherto adopted for the purpose.

In the methods hitherto employed the deposit of platinum obtained has been dull, and requires to be polished after being removed from the bath, whereas by this invention a deposit is obtained which is itself so bright that it requires no subsequent polishing. This feature constitutes in itself an important ad vantage effected by this invention, as the cost of polishing is entirely abolished.

The invention consists in the employment, with the abovementioned eleetro arrangements, of a bath made in the following manner: A solution of pure platinum metal is taken, or a solution of platinic ore in what is known as aqua-regia (nitrohydrochloric acid,) the platinum being dissolved in the usual manner, and the solution subsequently rendered neutral by any of the usual methods; or a solution of chloride of platinum may be employed. To this solution of platinum a weak solution of the ordinary phosphate of soda is added. A weak solution of the ordinary phosphate of ammonia is next added and the whole then boiled for several hours, and chloride of sodium solution added during such boiling.

The proportions of the above-named ingredients preferably used are as follows: One ounce chloride of platinum, twenty ounces phosphate of soda, four ounces phosphate of ammonia, one ounce chloride of sodium; the whole of the ingredients to be dissolved in sufficient water and used to make one gallon of solution.

The proportions may be varied, but those above given will produce good results.

The solution may be used at any suitable temperature, but preferably above the normal temperatn re of the atmosphere. A strong on r rent of electricity must be employed, and the cathode of the electric apparatus is preferably kept in motion during the operation of depositing the platinum. The battery-power required will depend upon the conditions above referred to; but I find that a current of about twelve amperes with an electro-motive force of about ten volts will give satisfactory results under most circumstances. The same bath may be employed'for a considerable time by keeping it up to its original strength by the addition of fresh platinum solution and chloride-ofsodium solution.

The duration of the exposure of the articles or surfaces to be coated to the act-ion of the electrolytic bath will depend on the temperature at which the operation is carried on, the distance between the anode and cathode, the nature of the current employed, and the thickness of coating desired, the density and degree of fineness of the deposit also naturally depending npon these conditions.

When desired to coat surfaces to which the platinum will not adhere directly, they must be first coated in any suitable manner with a substance to which platinum will adhere.

I am aware that phosphate of soda and phosph ate of potash in eonj auction with chloride of platinum have already been employed in baths for the electro-deposition of platinum, and I therefore lay no claim to the use of such substances in themselves, but only to the special bath containing the whole of the ingredients or substances above mentioned, and by which I am enabled to produce a more perfect result than has been efiected by processes hitherto employed or known. By the use of my improved bath I am able to produce a bright white deposit of platinum. of a fine close reguline nature of any desired thickness, and

2. The process of preparing a bath for platinuni electroplating, which consists in adding 15 to asolution of platinum a solution of phosphate of soda and a solution .of phosphate of ammonia, then boiling the solution so formed, and adding chloride of sodium during the operation, substantially as described.

lVILLIAM ARTHUR THOMS \Yitnesscs:

CHAS. A. ALLISON, HARRY A. M oLELLArI. 

